1. Field of the Invention
This invention relates to a process for the production of hoses having a plastic inner tube of reduced thickness.
2. Prior Art
Generally, hoses of laminated construction and smoothed inner periphery comprise an inner tube of thermoplastic resin, a rubber outer tube, a reinforcement and a rubber cover integrally superimposed one on another. Known hoses have been produced by inserting a mandrel through an inner tube performed of thermoplastic resin, and subsequently laminating a rubber outer tube, a reinforcement and a rubber cover in that order on the inner tube carried by the mandrel.
The prior art process however was encountered with the following problems:
1. Frequent flattening and kinking of the inner tube due to its thickness being small in the range of 50 to 800 microns, resulting in creased tube.
2. Impaired inner periphery of the inner tube due to frictional contact with the mandrel.
3. Limited external diameter and increased tolerance of the mandrel to fit smoothly into the preformed inner tube, leading to creased mandrel due to shrinkage during subsequent vulcanization.